1. Field of the Invention
This invention relates generally to a system for allocating resources for data streams and more particularly to a system for allocating transmission resources in a wireless system where the data includes an indication of its own resource needs.
2. Description of the Background
In networks and other arrangements, a situation often develops where a limited number of resources, such as bandwidth must be shared among a plurality of links. In particular, in a wireless type network, a number of mobile stations may be connected to a base station by wireless connections. Each base station may have only a limited number of channels to make these connections. Since many such mobile devices now utilize more than basic voice data, the amount of data which flows can vary substantially. Thus in addition to voice communications, wireless devices may include real time video, e-mail, web based information, etc. In order to fairly allocate the resources available, it is necessary for the base station to make some judgment as to which mobile stations can utilize the channels, and for how long.
The simplest arrangement, and one used largely in the past for voice data, is merely to dedicate a single channel for a single mobile station as long as it is connected. Only the assigned mobile station can use the channel. Depending on the original request, it is possible to assign more than a single channel but these multiple channels remain dedicated to that mobile station until the connection is terminated. No information is shared about the instantaneous amount of data waiting in the mobile station.
Another manner of handling the situation is to utilize a polling scheme where the base station polls each mobile station to learn the status of the data queue in each mobile station. This allows the base station to determine how to share the bandwidth resources among the different mobile stations. Thus, when polled the mobile station can send a response indicating whether it has data to transmit. For example, in a global system for mobile devices (GSM) time division multiple access (TDMA) system, the transmission opportunity for a mobile station is granted n frames after the base station receives the polling response from the mobile station, where n is the number of frames required to transmit a data block in the channel. Thus, there is a delay of multiple frames after polling, before an adjustment can be made.
Unfortunately, real time traffic such as video conference has unpredictable fluctuations in the data rate. Thus, any delay in adjusting the resources may mean that a link to a mobile station may not always have data in its transmission queue.
Since a dedicated channel assignment scheme does not allow any other mobile stations to use the channel when the assigned mobile station uplink queue is empty, the bandwidth assigned will not be used, which lowers overall spectrum efficiency. This leads to poor bandwidth utilization which will only get worse as the number of connections in the system increases. Also, during high data rate periods, the number of real time packets waiting in the uplink queue will increase. Due to the limited bandwidth, share assigned to the mobile station, packet congestion can occur and an increasing number of packets can exceed their delay requirements therefore decreasing the quality of service perceived by the end user.
While the polling scheme is more efficient than a dedicated channel assignment scheme from the perspective of bandwidth utilization, some bandwidth is still wasted because the mobile station cannot send actual data when sending a polled response. As polling becomes more frequency, more bandwidth is wasted. Further, additional delay is introduced because the packet has to wait while the poll is received and answered. Thus, the delay will further slow down transmission and counteracts any benefits gained by the polling.